The present invention relates generally to motor compressors and more particularly to arrangements whereby motor protection devices may be conveniently installed thereon.
Various arrangements have been used in order to secure thermally responsive motor protection devices to stator windings of motor compressors such as refrigeration compressors. In one of these various arrangements, a thermal sensor is secured directly to the stator windings by suitable ties generally fabricated from a plastic composition. This assembly is not totally satisfactory in that the ties often loosen during operation of the motor compressor unit due to the heat generated by the motor as well as the vibration encountered. This loosening may reduce the efficiency of heat transfer to the sensor, as well as enabling the sensor to vibrate against the windings causing deterioration of and possibly eventual failure of the insulation.
In another arrangement, the thermal sensors are embedded within the windings during fabrication of the stator assembly with electrical leads being brought out of the assembly along with the stator coil leads. While this arrangement overcomes the loosening problem associated with the externally secured protection device, it requires additional control circuitry to be installed and connected as these sensors are relatively small and of low current carrying capability. The addition of other control components not only increases costs of assembly in that they require additional connections to be made but also represent additional potential sources for system failure.
Accordingly, the present invention overcomes these disadvantages in providing a motor protection assembly in which the motor protection device is secured to and retained in heat transfer relationship with the stator windings by a motor cover substantially enclosing the end turns of the stator. The protection device is secured to the motor cover in such a manner as to allow the distance which the protection device protrudes into the interior of the cover to be varied thereby enabling a standard sized cover and protector assembly to be used on different size stator assemblies. Further, as the protection device can project outward beyond the motor cover, a greater space is available so as to enable the use of line break protection devices which can be directly connected to the motor winding circuit without the need for separate control circuitry. This feature offers the advantages of improved reliability due to the need for fewer components as well as reduced cost both in materials and labor. Additionally, the protection device electrical connections are entirely within the outer shell thus eliminating the need to provide additional fusite connectors as well as enabling a smaller external terminal box to be employed and eliminating the possibility of unauthorized tampering with the protector connections. Further, the present invention is well suited for assembly line assembly as the positioning of the protector with respect to the stator is controlled so as to substantially eliminate the possibility that the protector may be secured in an incorrect position on the windings as well as eliminating the possibility of winding ties being over or under stressed.
Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims taken in conjunction with the accompany drawings, which set forth by way of illustration and example the preferred embodiments of the present invention.